Cushioning mechanism



Aug. `25, 1936. l.. M. CLARK CUSHIONING MECHANISM Filed July 19, 1935 2 sheets-sheet 2 ATTORNEYS Patented Aug. '25, 1936 This invention relates to-cushioning mechanism of the energy absorbing type and is concerned m'ore particularly wth a novel friction cushioning mechanism which may be employed for various purposes, as, for example, as a draftl gear for railway equipment, or in connection with buffers, trucks, etc. While the new cushioning mechanism has a wide range of utility, it may be employed to especial advantage as a draft gear, and accordingly an embodiment of the invention for that purpose will be illustrated and described to makeclear the principles of the invention. s

As is well known, draft gears are commonly employed on railway vehicles to protect their structures and lading against shocks to which they are subjected during switching and when in train service, and one of the objects of my invention is to provide a cushioning mechanism which is suitable for use as a draft gear and which has high energy absorption. low resistance, smooth action,` and sustained initial compression. In addition to these features, the new device is of rugged construction so that it has along life, and it is of relatively light weight.

The new cushioning mechanism comprises a casing preferably cylindrical in form which encloses the operating elements of the device and is provided in one end with the friction generat ing surface of frusto-conical formation. Fricspaced relation, and a partially compressed coil spring within the casing engages the inner face of the ring and tends to force it and the shoes outwardly. The force of the spring is transmitted from' the shoes through the interengaging parts to the plunger and the`outward movement of the latter is limited by appropriate means, such as a tie bolt.

The interengaging parts on the shoes and plunger are of such form that when a compressive force is applied to the device, the shoes move inwardly along the friction surface, generating friction and compressing the spring. When the force is removed, the expansive stresses in the casing react against the shoes and effect the release of the device and the spring thereupon restores the parts to their original position. While the spring functions to maintain the initial compression of the cushioning mechanism and to ing of that shape permits expansive stresses to maintain the device at its normal full length,` it doesnot react against the plunger and therefore does notfunction as a releaseV spring. In order that the-expansive stresses of the casing may be effective to release the device, the interengagingA 5 parts on the shoes and .plunger are of angular formation and the angles involved are of the type known as self-releasing angles.

'Ihe spring employed may be either vsingle or y 'double and it is so arranged that the torsional 10 force of the spring, exerted during its operation of restoring the device to normal condition after removal of a compressive force, acts, on the ring and causes the ring to move circumferentially. This movement of the ring causes the group of l5 shoes to be shifted circumferentially with the result that successive inward movements of the shoes along the friction generating surface are on diii'erent parts of the surface and the formation of grooves which extend lengthwise of the sur- 20 face and are of arcuate cross-section and which would result lin improper functioning of the device under certain conditions hereinafter described, is prevented.

For a better understanding of the invention, 25 reference may be had to the accompanying drawings in which- Fig. 1 is a view in. longitudinal section of the device as used as a draftgear;

Fig. 2 is a View similar to Fig. 1, showing the 30 device under compression and with ce of the parts illustrated in elevatiom' Figs. 3 and. i are sectional views on the lines 3--3 and t--ii of Fig. l., respectively;

Fig. 5 is a fragmentary sectional view showing the shoes in elevation;

Fig. d is an end view of a part of the device;

Fig. 'I is a view of the inner surface of one shoe; and

Fig. is a sectional View lon the line t-t of Fig. 7.

Referring new to the drawings, the device is illustrated in lig. 1 as comprising a casing it, preferably of cylindrical formation, since a cashe readily equalizer?. so that the casing, even though of light weight, is not liable to burst. At one end, the casing is closed and'this end of the casing is provided with anges i i and it of generally rectangular shape, as shown in Fig. 3. in the installation shown in Fig. l, the casing lies hetween the usual draft sills i3 of a railway car and the flanges il i. and i2 engage stop lugs it secured to the inner surfaces of the sills. The opposite end. of the casing is open and adjacent this open end, the inside of the casing is formed with a friction-generating surface 'I5 of frustoconical formation. This surface is of sufficiently large area to obtain the necessary cushioning capacity without undue abrasion,` and the inward taper of the surface is selected to provide the proper rate of capacity increase of the device in operation.

Mounted within the casing at the open end are friction shoes i6, each of these shoes being arcuate in section and having its outer curved surface in contact with the friction-generating surface I5 of the casing. The curvature of the friction surfaces of the shoes is so related to the curvature of the frictionegenerating surface I5 ln the casing, that maximum contact is obtained when the shoes are at the limit of their inward movement into the casing. 'I'he shoes are arranged in a circular series and each shoe has angular projections I1 on Iits inner surface, the shoes as illustrated being provided with three such projections which extend across the shoe, each projection having sloping surfaces I8 which are convergent toward the top of the projection. At its inner end, each shoe is provided with a notch i9, and at the inner end of the group of shoes is a fiat ring 20 which is formed with a circular stiffening rib 2| from which extend radial ribs 22 on equal spacing with each rib 22 entering a notch i9 in a shoe. Acoil spring 23 within the casing bears at one end against the closed end of the casing and at the other end against the inner surface of the ring 20, and this spring may be single, or double, as illustrated. If a double spring is employed, both component parts have the same twist. If desired. the end of the spring which bears against the closed end of the casing may have an offset portion 24 which enters an opening 25 in the end wall of the casng.

inside the group of shoes is an actuating plunger' 26, which is of generally cylindrical formation and has circumferential corrugations 21 on its outer surface. Each corrugation lies between adjacent projections il on the shoes and has sloping surfaces 28 corresponding to the sloping surfaces I 8 on the projections. The plunger has an end portion 29 of reduced diameter which extends through a ycentral opening in the ring 20 and servesv as an axial guide for both the ring and the spring. A tie bolt 30, the head of which is seated in an opening in the end wall of the casing, passes through a bore in the end portion 29 and has a nut 3| on its end, the nut lying inside and engaging a portion of the plunger.

When employed as a draft gear. the device is used with the usual front follower 32, the rear face of which normally engages the end of the plunger 20, and the usual coupler shank 34 bearing against the front face of the follower 32 is provided. The forward end of the casing I 0 is engaged by the rear face of front follower 32 when the device is fully closed as shown in Fig. 2.

As assembled, the friction shoes i6, which are preferably six in number so as to obtain uniform pressure distribution, project out of the casing, and the inclined surfaces thereon are forced into contact with corresponding surfaces on the plunger by the force of the spring 23 transmitted to the shoes through the ring 20. The outward movement of the plunger being limited by the tie bolt 30, the shoes are forced radially outward against the casing. 'Ihe compressed spring com.- bined with the pressure of the shoes against the casing interior establishes-the initial resistance of the device. Since the free length of the spring is considerably greater than its length Vwhen the device is in normal or released position, it is obvious that the result of any normal set" combined with such lengthening as is occasioned by .the outward movement of the shoes compensating for casing bore wear will not materially eect spring loading values.` Consequently, the initial resistance of the device will remain essentially uniform throughout its life. This effect could not be obtained with springs of high ultimate capacity such as are required in the majority of high capacity friction devices.

In the operation of the-device, its overall length is shortened by the plunger being forced into the casing, carrying the shoes with it and thereby generating friction. In draft, the casing I0 is moved over the shoes i6 and plunger 26 by the rear end of yoke 35 being drawn forward by the coupler 34, while in buff, the shoes I8 and plunger 26 are moved into the casing i0 by the coupler shank 34 acting against the follower 32. The inward movement of the plunger and shoes takes place against the resistance of the spring and the force of the spring acting through the angular formations of the shoes and those on the plunger tends to force the shoes radially outward. Friction between the shoes and conical surface in the casing is developed in part by the action of the spring tending to force the shoes outwardly and in part by the decreasing diameter of the surface along which the shoes move. 'I'he angular formations on the shoes and plunger are such that there is a radial clearance at all times between the shoes and plunger so that the mechanism can be fully closed without jamming which would otherwise result in failure to release.

vIn the normal or released position of the mechanism, the helical spring exerts a pressure of the order of 6,000 to 7,000 pounds and this pressure, acting through the interengaging projections of shoes and plunger, forces the former radially outward against the conical surface in the cylinder, and offers resistance to inward movement of the shoes and constitutes what is known as the initial compression of the mechanism. Whenever a force of sumcient magnitude is applied to the cushioning device to overcome its initial compression, the plunger, shoes, and spacing ring, are moved into the casing with the result `that the casing is subjected to expansive stresses. During the inward movement of the shoes, the radial pressure tends to increase until the reaction of the casing under expansion, op erating through the coacting angular formations on the shoes and plunger, overcomes the static adhesion and forces the shoes inwardly with respect to the plunger. This results in the reduction of the effective outside diameter of the group of shoes and correspondingly reduces the pressure of the shoes against the casing. In certain prior devices of this sort, the static adhesion of the parts is so great that the inwarding acts through the shoes tocause the plunger to be expelled slightly with4 respect to the shoes. The pressure of the shoes against the casing is thereupon reduced to that arising from the' actionof the coil spring, and since the frictional vengagement of the shoes and casing can be overcome by that component of the spring force which is directed outwardly, the spring acts at once to restore the operating parts to their normal Vor release position, Y

The spring employed has a relatively high capacity' in the normal condition of the device and its capacity -does not greatly increase during the closingV of the cushioning mechanism, with the result Vthat a yrelatively small amount of energy is stored in the spring during closure of the device and subsequently deliveredin the form of theshoes wearing grooves lengthwise of the friction surface and of-a cross-sectional shape corresponding to that of the shoes. In devices in which such groove wear takes place. the expansive stresses ultimately become unbalanced and the casing may prematurely fail .in service. Also in devices in which the friction surface on the casing becomes so grooved, a blow of unusually high'magnitude will accasionally cause the shoes to become displacedv circumferentially with the result that the Ashoes may contact in part withthev intervening ridges of relatively small area, lDuring subsequent closure of the mechanism, sumcient heat maybe developed on the resultant small areasv of contact to cause the shoes and casing to become partially welded together duc to excessive heat, with the result that the mechanism fails to release.

In the present device, the spring'acting on the spacing ring causes 'no circumferential movement of the latter during closing of the device because the pressure of the friction shoes against the friction surface on the casing offers too great a resistance. Accordingly, during closing, the torsional movement of the spring results in a slippage of the spring over the face of the ring ,of the mechanism.

l The device of the application adords an additional advantage in that it may readily be asy sembled and taken apart without the application of high pressures. With other types of devices of the saine general character, pressures ranging from 25,000 to '75,000 poundsl must be applied to compress the devices sumciently against their combined spring and frictional resistance to permit the removal of the nuts, keys, or other means that are used to hold the devices at their normal assembled lengths. Such relatively high pressures usually require that the 'devices be delivered to shops where hydraulic presses or similar facilities are available for v.theapplication of the pressures, wheneverthe devices are to be taken apart. This 'involves expenditures of both time and money. s

In the device of the application, it will be noted that the frictionshoes project outwardly beyond the open vend of` the housing and the direct inward movement of the shoes is resisted only by the helical spring acting through the spacer ring. Accordingly, by 'applying pressure directly to the ends of the shoes by means of a suitable device such as a sleeve or, the like, the shoes can be forcedlnwardly to an extent suillcient to permit readyremoval of the nut 3i on theend of the tie bolt and the pressure required f or this purpose is oi" the order of 6,000 to 7,000 pounds. The use of such a sleeve permits the pressure to be applied directly to the shoes and not to the end of the plunger,and a suitable sleeve for the purpose may have a window or other means through which access to the tie bolt nut may be had. The sleeve may be employed both for dismantling and assembling the device and by'its use, these operations are simpliiledandmade relatively easy.

l. A cushioning mechanism of the friction type, which comprises a casing, friction shoes therein, a central actuating plunger extending within the group of shoes, a plurality of cooperating wedging surfaces' on both the inner surfaces of said shoes and the outer surface olsaidplunger, said surfaces being distributed along the length of said sho'es and plunger, a ring engagingtsaid shoes and maintaining them in proper circumferentially spaced relation, and a spring within said casing engaging said ring and resisting inward movement thereof.

2; A cushioning mechanism of the friction' type which comprisesa casing, friction shoes therein, a central actuating plunger extending within the group of shoes, a plurality of cooperating interengaging wedging parts on both the inner surfaces of said shoes and the outer surface of said plunger, said surfaces being distributed along the length of said shoes and plunger, a ring cngaging the shoes andmaintaining them in proper circumferentially spaced relation, and a 4spring Within said casing engaging said ring and resisting inward movement thereof.

. 3. A cushioning mechanism of the friction type which comprises a casing, friction shoes therein, a central actuating plungerextending within the group of shoes, a plurality of interengaging wedglof said shoes interlocked With the shoes and maintaining them in proper circumferentially spaced relation, and-a spring within said casing engaging the ring and resisting inward movement thereof. v

d. Acushioning mechanism ofthe friction type which comprises a casing, a friction surface in said casing, friction shoes in the casing Acontacting with said surface, alcentral actuating plunger, said plunger and shoes having a plurality of engaging surfaces inclined to the axis of the casing, and distributed along the length of said shoes taining them in proper circumferentially Aspaced relation, and a spring within said casing engaging the ring and resisting inward movement.

thereof.

5. A cushioning mechanism of the friction type, I

which Acomprises a casing, a friction surface in said casing, friction shoes in the casingf'contacting with said surface, a central actuating plunger extending within the group of shoes, said shoes and plunger having engaging'surfaces inclined to the axis of the casing at self-releasing angles, said engaging surfaces lying both on the outer surface of said plunger and on the inner surfaces of said shoes and being distributed lengthwise thereof, a ring at the inner ends of said shoes engaging said shoes and maintaining them in proper circumferentially spaced relation, and a spring Within the casing engaging the ring and resisting inward movement thereof.

6. A cushioning mechanism of the friction type which comprises a casing having a closed end and an open end and a friction surface adjacent said open end and of progressively decreasing diameter inward from said end, a plurality of friction shoes in a circular series engaging said surface, a central actuating plunger extending within the group of shoes and having parts interengaging with parts on the shoes, said parts on the shoes and plunger being arranged in tandem lengthwise of said plunger and shoes, a ring at the inner ends of the shoes and interlocked therewith to maintain said shoes in proper circumferentially spaced relation, and a coil spring bearing at one end against said ring and tending to force said ring out of the casing.

7. A cushioning mechanism of the friction type which comprises a casing having a closed end and an open end and a friction surface adjacent said open end and of progressively decreasing diameter inward from said end, a plurality of friction shoes in a circular series engaging said surface, a central actuating plunger extending within the group of shoes and having parts interengaging with parts on the shoes, said parts on said plunger and shoes being of wedge formation and distributed in tandem on said plunger and shoes, a ring at the inner ends of the shoes and interlocked therewith to maintain said shoes in proper circumferentially spaced relation, and a double coil spring bearing against said ring and tending to force said ring out of the casing, both coils of said spring being wound in the same direction. v

8. A cushioning mechanism of the friction type which comprises a casing formed with an interior friction surface, a plurality of friction shoes in the casing engaging said surface, a ring at the inner end of the group of shoes and engaging the latter to maintain them in proper circumferentially spaced relation, a central actuating plunger within the group of shoes and having parts interengaging with parts on said shoes, and a helical spring within the casing bearing against said ring and tending to force it out of the casing, said plunger having an end portion of reduced diameter passing through an opening in said ring and entering said spring, said end portion serving as an axial guide for said ring and spring.

9. A cushioning mechanism of the friction type which comprises a casing formed with an interior friction surface, a plurality of friction shoes in the casing engaging said surface, a ring at the inner end of the group of shoes andengaging the latter to maintain them in proper circumferentially spaced relation, a central actuating plunger within the group of shoes and having'parts interengaging with parts on said shoes,

and a helical spring within the casing bearing at one end against said ring and tending to force it out of the casing, the other end of the spring being anchored.

l0. A cushioning mechanism of the friction type, which comprises a casing closed at one end and open at the other, a frusto-conical friction surface on the inner surface of said casing, a plurality of friction shoes engaging said surface and lying side by side, an actuating plunger extending within the group of shoes, said plunger and shoes having interengaging parts provided with contacting surfaces inclined to the longitudinal axis of the casing, the inclination of said surfaces being at self-releasing angles and one end of said plunger projecting out of the casing, said interengaging parts being distributed in tandem lengthwise of said shoes and plunger, a disc at the ends of said shoes provided with means engaging the shoes and maintaining them in proper circumferentially spaced relation, and a helical spring engaging said disc and tending to force it outward.

1l. A cushioning mechanism of the friction type which comprises a casing of cylindrical form having a closed end and an open end, flanges at the closed end of the casing lying in a plane transverse to the axis of the casing, a friction surface on the inner wall of the casing, said surface being of progressively decreasing diameter toward the interior of the casing, friction shoes in the casing arranged in a circular series and engaging the friction surface, a central actuating plunger within the series of shoes, said plunger and shoes having interengaging parts, a ring at the inner end of the series of shoes having parts interengaged with individual shoes for maintaining said shoes in proper circumferentially spaced relation, a spring engaging the ring and tending to force it out of the casing, and means limiting the outward movement of said plunger.

l2. A cushioning mechanism of the friction type which comprises a casing, friction shoes therein arranged in a circular series, a central actuating plunger extending within the group oi' shoes, a plurality of interengaging wedging parts on both said shoes and plunger, the parts on said shoes being formed on the inner surfaces thereof, and the parts on said plunger being formed on the outer surface thereof and extending circumferentially of said plunger, said parts on the plunger being disposed along the length of the latter, a ring engaging said shoes and maintaining them in proper circumferentially spaced relation, and a spring within said casing engaging said ring and resisting inward movement thereof.

13. A cushioning mechanism of the friction type which comprises a casing, friction shoes therein arranged in a circular series, a central actuating plunger extending within the series of shoes,r transverse wedging parts on the inner surfaces of said shoes, wedging'parts extending circumferentially on the outer surface of said plunger, said parts being arranged in series lengthwise of said plunger and shoes, a ring engaging the shoes and maintaining them in proper circumferentially spaced relation, and a shoes, interlocking wedging parts on the inner A spring within said casing engaging said ring and resisting inward movement thereof.

14. A cushioning mechanism of the friction type which comprises a casing, friction shoes therein arranged in a circular series, a central actuating plunger extending within the series of surfaces of said shoes and on the outer surface of said plunger, said parts on said plunger lying 'in rows extending lengthwise of said plunger, a

ring engaging said shoes and maintaining them in proper circumferentially spaced relation, and

a spring within said casing engaging said ring 5 and resisting inward movement thereof.

IEV'EREIT M. CLARK. 

